The Ripple Effects of Closing Locks and Dams on the Mississippi

By Bob Filipczak

The dynamics of a river are complex and far-reaching, and when you are talking about a river the size of the Mississippi, the ramifications are amplified. And the dynamics of the upper Mississippi in Minneapolis and St. Paul could be changing quickly.

The first indicator of this was when U.S. Army Corps of Engineers, which operates the lock and dam system in the Twin Cities, closed the lock at upper St. Anthony Falls in Minneapolis. This was due to the passage of the Water Resource Reform and Development Act of 2014, and it was closed to prevent the further spread of an invasive species of carp. It closed in June 2015 and it is the furthest north lock and dam on the river.

The remaining two locks and dams are still open, but the Corps is working on a study that may make a recommendation to close the lower St. Anthony lock and dam as well as Lock and Dam # 1 in St. Paul, a few miles downstream. The study, an initial assessment and disposition study, was triggered by the closing of the first lock and dam.

The assessment and disposition will look at whether the Army Corps of Engineers should continue to operate these three units. Nanette M. Bischoff, P.E., is the Project Manager/FERC Coordinator for the St. Paul District Corps of Engineers, and this is her project. She explains that they were authorized to do the study by section 216 of Flood Control Act of 1970.

The results aren’t complete yet, but it doesn’t look like a case can be made to continue to operate the lock and dam system in the upper Mississippi. “We’ve gone from closing the upper lock to potentially getting rid of these sites in a couple of years,” says Bischoff.

The study looks at the expense of operating the three locks and dams weighed against the traffic and commercial benefits of these navigational structures. In short, there’s just not enough commercial traffic to justify operating the three locks and dams. The only barges that use the locks currently, says Bischoff, are the ones MnDOT brings through for bridge maintenance. Kevin Western, state bridge engineer for MnDOT said, “the possibility of the locks completely closing would greatly increase cost and challenge our abilities to maintain and rehab these structures.”

What’s Next

If the disposition comes to the conclusion that this trio of locks and dams is no longer cost-effective (it costs about $3 million a year), the recommendation goes up the chain of command to the Assistant Secretary of the Army for Civil works. If he or she accepts the recommendation, she refers it to Congress. Only Congress can close the remaining locks and dams on the upper Mississippi by deauthorizing them. Once deauthorized, they cannot be used for navigation anymore.

If Congress approves closing the units, the ownership of the land and structures goes to the U.S. General Services Administration. A bunch of federal procedures then go into effect to find new owners for the three units. Some possibilities have already emerged, even though closing the locks is not a certainty.

The Friends of the Lock and Dam, for example, are envisioning an interpretive center for the upper St. Anthony Dam. In that proposal, says Bischoff, the National Park Service would probably be interested in being part of the project.

All three locks and dams are being considered for hydropower, and proposals from Crown Hydro have been submitted. There’s already some hydropower being generated at the lower St. Anthony dam.

One of the more controversial proposals comes from American Rivers, an environmental activist organization that is suggesting that Lock and Dam #1 be completely removed. This would potentially restore the Mississippi River Gorge, a wild section of river that would put a fast-moving river including rapids right in the middle of Minneapolis and St. Paul.

As Bischoff explains, there is a 36-foot drop between lower St. Anthony Falls and Lock and Dam #1. That could make for some very swift currents if the lock is removed.

While the upper St. Anthony lock and dam is closed, it can be operated by the Corps in the case of flooding. In that case, says Bischoff, they would bring in a crane to remove the in-place bulkheads to relieve any flooding, especially during spring runoff.

Closing a Lock and Dam

The physics and logistics of shutting down a lock and dam aren’t as onerous as you might imagine. Once the bulkheads went into place, explains Bischoff, the miter gates were tied back into their recesses. The tainter gate will be in place for flood control.

After that, there’s not much to it. The concrete is all in pretty good shape and “generally it’s pretty easy to maintain if you can keep the graffiti artists off of it,” says Bischoff.

It’s important to remember that Congress has deauthorized locks and dams before. Some examples are:

Savannah Bluff Lock and Dam

Willamette Falls Lock

Green River dam

However, the size of units in the Twin Cities make this rather unprecedented. This is, after all, the Mississippi River we are talking about. Closing three locks and dams on the largest river in the U.S. is a major decision. Last time a lock was closed on this river was in 1917 when they were building Lock and Dam #1. It is currently the deepest lock on the whole river with a 49.5-foot drop.

So big decisions are ahead for the uppermost locks and dams on the Mississippi. The recommendation that is likely to come at the end of the disposition is to close the units. But a lot could happen between that recommendation and any action from Congress. Unlike a lot of federal projects that move slowly, however, the future of the locks and dams are picking up speed. Says Bischoff, “Some decisions are being made pretty rapidly, and things can change quite dramatically especially at the upper locks in the next couple of years.”